Please! I need help in Chemistry, and explain it to me?
What is the morality of a solution containing 20 grams of NaOH in 500 millimeters of solution?
(1) 1 M
(2) 2 M
(3) 0.04 M
(4) 0.5 M
Answer:
Obviously, you mean “Molarity” instead of “morality” (that is probably Spell-check’s mistake).
Anyway,
Molarity is a measure of concentration of a solution.
Molarity is defined as,
Molarity = Moles of solute / Liters of solution
So to find the molarity of the NaOH solution the question asked about, you need to know two pieces of information….the number of moles of the solute (which is NaOH in this case) and the number of liters of solution.
We are told that the solution has a volume of 500 mL, which is equal to 0.5 Liters.
We now need to find the number of moles of NaOH dissolved in this solution.
We are told that 20 grams of NaOH are in solution, so how many moles is this?
To find out the number of moles of NaOH in a given number of grams, simply divide by the molar mass of NaOH.
To find the molar mass of NaOH from the periodic table, add up the molar masses of each of the elements which make it up.
There is 1 Sodium atom/ion (22.99 g/mol) in NaOH, plus 1 Oxygen atom (16 g/mol), plus 1 Hydrogen atom (1.01 g/mol). Add all these together and you get 40 g/mol.
Moles of NaOH = 20 g NaOH / (40 g/mol NaOH)
Moles = .5 NaOH
So we have .5 moles of NaOH dissolved in .5 Liters of solution.
We can now find the molarity.
Molarity = .5 moles of NaOH / .5 Liters of solution
Molarity = 1 Molar
Which is choice (1)
Of course NaOH means sodium, with oxygen/hydregen.
if you have 20 grams of that in 500 millimeters the solution for me would be (4)
(3) 0.04
I assume you mean molarity, as opposed to morality.
Well ...
NaOH has a molar mass of roughly 40 g/mol (39.997 if you want to be precise). Therefore, we have approximately
20mol / 40 g/mol = 0.5 mol of sodium hydroxide present
All that is left is to work out the concentration of the sodium hydroxide, and this is a fairly easy calculation.
0.5 mol / 500 mL = 0.5 mol / 0.5 L = approx. 1 M
Hope this helps. Good luck in your studying.
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